1. Field of the Invention
This invention relates to a method of removing catalyst-poisoning impurities, or contaminants; such as, arsenic or selenium; from hydrocarbonaceous fluids; such as, synthetic crude oil and synthetic oil fractions.
2. Description of the Prior Art
There has been a resurgence of interest in sources of energy that were formerly noncompetitive. These sources of energy include shale oil, fluids obtained from coal, bitumen obtained from tar sands, and the like. Many of these hydrocarbonaceous (i.e., not composed exclusively of hydrogen and carbon) fluids contain contaminants that could poison expensive catalysts, such as those used in hydrogenation and other processes to which these hydrocarbonaceous fluids must be subjected before they can be satisfactorily transported and used as sources of energy. The best prior art of which I am aware is disclosed in a co-pending application Ser. No. 314,015, filed Dec. 11, 1972 now abandoned in favor of Ser. No. 421,139, filed Dec. 3, 1973, with co-inventor Donald K. Wunderlich and entitled "Synthetic Oil Treatment." That descriptive matter will be briefly summarized hereinafter for the reader's convenience. The prior art has included a method for removing arsenic from hydrocarbon charge stocks, such as described in U.S. Pat. No. 2,778,779. Such methods have included using the iron, nickel and cobalt oxides to remove arsenic from streams of naturally occurring crude, such as naphtha or straight run gasoline. By employing the oxides at low temperature, such as from room temperature to about 200.degree.F, by disregarding the atmosphere under which the reaction takes place, and by using substantial amounts of water, the oxide acts as an oxidizing agent and oxidizes the arsenic to a water soluble arsenic oxide. In this way the arsenic oxide is dissolved in the water and removed from the naturally occurring crude oil or oil fraction.
Also, arsenic has been removed from similar naturally occurring crude oils by contacting them with a metallic salt of a strong acid at low temperature, such as room temperature, without regard to the atmosphere under which the contacting takes place. In this particular process, it was taught that oxides do not work for removing arsenic and this process is disclosed in U.S. Pat. No. 2,781,297.
Processes that work for removing other contaminants, or catalyst-poisoning materials, such as organo-metallic compounds like iron porphyrins, are frequently inoperable for removing impurities like arsenic. For example, the catalytic hydrogenation of hydrocarbons to effect the precipitation of an insoluble iron salt of the iron prophyrin within a hydrogenating catalyst, as described in U.S. Pat. No. 3,496,099, cannot be employed satisfactorily in removing arsenic from synthetic crudes of the like.
The invention described in Ser. No. 314,015 improved significantly on the prior art, but had one drawback that prevented its being totally satisfactory. The contaminant tended to be concentrated in a surface layer about 30 microns thick, so the center portion of the larger pellets and the like were not useful and available for removing the contaminant.
In fact, none of the prior art processes have been completely satisfactory in removing catalyst-poisoning impurities, such as arsenic, from synthetic crude oil and synthetic oil fractions.